Porous electrode substrate and production method therefor

Abstract

Provided is a porous electrode substrate capable of reducing a drop in electromotive force when used in a battery. This porous electrode substrate comprises a carbon fiber sheet wherein carbon fibers are bound by a binder. For dust of 0.3 μm or more in particle size, the dust generation amount per 1 m 2 of the porous electrode substrate is 120,000/m 2 or less, as determined by the following method: dust particles in a gas obtained by suctioning at 47.2 mL/s for 40 minutes using a dust collecting hood having an opening of 500 mm×100 mm while traveling the sheet at a speed of 10 m/min from a position 200 mm below the sheet are used; the number of dust particles having a diameter within a predetermined range is measured by a particle counter; and the measured value is divided by 200 m 2 , which is a suction area, and the resulting value is defined as a dust generation amount per 1 m 2 .

The invention claimed is: 
     
       1. A porous electrode substrate comprising a carbon fiber sheet in which carbon fibers are bound by a binder, wherein the carbon fibers have an average fiber diameter of 4 to 20 an average fiber length of 2 to 30 mm, a tensile elastic modulus of 200 to 600 GPa, and a tensile strength of 3,000 to 7,000 MPa; for dust having a particle size of 0.3 μm or more and less than 0.5 the dust generation amount per 1 m 2  determined by the following method is 1 to 50,000 particles/m 2 ;
 the dust generation amount per 1 m 2  determined by the following method for dust having a particle size of 0.5 μm or more and less than 1.0 μm is 1 to 30,000 particles/m 2 ; 
 the dust generation amount per 1 m 2  determined by the following method for dust having a particle size of 1.0 μm or more and less than 2.0 μm is 1 to 20,000 particles/m 2 ; 
 the dust generation amount per 1 m 2  determined by the following method for dust having a particle size of 2.0 μm or more and less than 5.0 μm is 1 to 10,000 particles/m 2 ; and 
 the dust generation amount per 1 m 2  determined by the following method for dust having a particle size of 5.0 μm or more is 1 to 5,000 particles/m 2 :
 dust particles in a gas obtained by suctioning at 47.2 mL/s for 40 minutes using a dust collecting hood having an opening of 500 mm×100 mm while traveling the sheet at a speed of 10 m/min from a position 200 mm below the sheet are used; the number of dust particles having a diameter within a predetermined range is measured by a particle counter; and the measured value is divided by 200 m 2 , which is a suction area, and the resulting value is defined as a dust generation amount per 1 m 2 . 
 
 
     
     
       2. The porous electrode substrate according to  claim 1 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.3 μm or more and less than 0.5 μm is 50,000 particles/m 2  or less. 
     
     
       3. The porous electrode substrate according to  claim 1 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.5 μm or more and less than 1.0 μm is 30,000 particles/m 2  or less. 
     
     
       4. A porous electrode substrate comprising a carbon fiber sheet in which carbon fibers are bound by a binder, wherein for dust having a particle size of 0.3 μm or more, the dust generation amount per 1 m 2  determined by the following method is 120,000 particles/m 2  or less:
 dust particles in a gas obtained by suctioning at 47.2 mL/s for 40 minutes using a dust collecting hood having an opening of 500 mm×100 mm while traveling the sheet at a speed of 10 m/min from a position 200 mm below the sheet are used; the number of dust particles having a diameter within a predetermined range is measured by a particle counter; and the measured value is divided by 200 m 2 , which is a suction area, and the resulting value is defined as a dust generation amount per 1 m 2 . 
 
     
     
       5. The porous electrode substrate according to  claim 4 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 1.0 μm or more and less than 2.0 μm is 20,000 particles/m 2  or less. 
     
     
       6. The porous electrode substrate according to  claim 4 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 2.0 μm or more and less than 5.0 μm is 10,000 particles/m 2  or less. 
     
     
       7. The porous electrode substrate according to  claim 4 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 5.0 μm or more is 5,000 particles/m 2  or less. 
     
     
       8. The porous electrode substrate according to  claim 4 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.3 μm or more and less than 0.5 μm is 1 to 50,000 particles/m 2 ;
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.5 μm or more and less than 1.0 μm is 1 to 30,000 particles/m 2 ; 
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 1.0 μm or more and less than 2.0 μm is 1 to 20,000 particles/m 2 ; 
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 2.0 μm or more and less than 5.0 μm is 1 to 10,000 particles/m 2 ; and 
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 5.0 μm or more is 1 to 5,000 particles/m 2 . 
 
     
     
       9. The porous electrode substrate according to  claim 4 , wherein the carbon fibers have an average fiber diameter of 4 to 20 μm, an average fiber length of 2 to 30 mm, a tensile elastic modulus of 200 to 600 GPa, and a tensile strength of 3,000 to 7,000 MPa. 
     
     
       10. A porous electrode substrate comprising a carbon fiber sheet in which carbon fibers are bound by a binder, wherein for dust having a particle size of 0.3 μm or more, the dust generation amount per 1 m 2  determined by the following method is 200,000 particles/m 2  or less:
 dust particles in a gas obtained by suctioning a range of 50 mm in diameter at 47.2 mL/s for 10 seconds at any five different positions 50 mm or more away from the end of the sheet are used; the number of dust particles having a diameter within a predetermined range at the respective positions is measured by a particle counter; the each measured value is divided by 0.0020 m 2 , which is a suction area; and an average value of the resulting values obtained in the five different positions is defined as a dust generation amount per 1 m 2 . 
 
     
     
       11. The porous electrode substrate according to  claim 10 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.3 μm or more and less than 0.5 μm is 100,000 particles/m 2  or less. 
     
     
       12. The porous electrode substrate according to  claim 10 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.5 μm or more and less than 1.0 μm is 50,000 particles/m 2  or less. 
     
     
       13. The porous electrode substrate according to  claim 10 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 1.0 μm or more and less than 2.0 μm is 10,000 particles/m 2  or less. 
     
     
       14. The porous electrode substrate according to  claim 10 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 2.0 μm or more and less than 5.0 μm is 10,000 particles/m 2  or less. 
     
     
       15. The porous electrode substrate according to  claim 10 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 5.0 μm or more is 3,000 particles/m 2  or less. 
     
     
       16. The porous electrode substrate according to  claim 10 , wherein the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.3 μm or more and less than 0.5 μm is 1 to 100,000 particles/m 2 ;
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 0.5 μm or more and less than 1.0 μm is 1 to 50,000 particles/m 2 ; 
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 1.0 μm or more and less than 2.0 μm is 1 to 10,000 particles/m 2 ; 
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 2.0 μm or more and less than 5.0 μm is 1 to 10,000 particles/m 2 ; and 
 the dust generation amount per 1 m 2  determined by the method for dust having a particle size of 5.0 μm or more is 1 to 3,000 particles/m 2 . 
 
     
     
       17. The porous electrode substrate according to  claim 10 , wherein the carbon fibers have an average fiber diameter of 4 to 20 μm, an average fiber length of 2 to 30 mm, a tensile elastic modulus of 200 to 600 GPa, and a tensile strength of 3,000 to 7,000 MPa. 
     
     
       18. A method for producing a porous electrode substrate according to  claim 4 , comprising the following steps [1] to [3]:
 step [1]: driving the carbon fiber sheet in which carbon fibers are bound by a binder with holding on a roll having a diameter of 20 to 350 mm along the sheet flow direction, 
 step [2]: applying a rotary brush to a portion of the carbon fiber sheet held on the roll in step [1], and 
 step [3]: removing dust on a portion of the carbon fiber sheet to which the rotary brush has been applied in step [2]. 
 
     
     
       19. The method for producing a porous electrode substrate according to  claim 18 , wherein the holding angle of the roll in step [1] is 2 to 180°. 
     
     
       20. A method for producing a porous electrode substrate according to  claim 10 , comprising the following steps [1] to [3]:
 step [1]: driving the carbon fiber sheet in which carbon fibers are bound by a binder with holding on a roll having a diameter of 20 to 350 mm along the sheet flow direction, 
 step [2]: applying a rotary brush to a portion of the carbon fiber sheet held on the roll in step [1], and 
 step [3]: removing dust on a portion of the carbon fiber sheet to which the rotary brush has been applied in step [2].